The present invention relates to a semiconductor device such as a CCD (Charge Coupled Device) type solid state image pickup device in which it is required to transfer signal charges in a depletion region (channel) formed under electrodes with high signal charge transfer efficiency.
A method of improvement of charge transfer speed and transfer efficiency of a semiconductor device composed of a plurality of electrodes formed on a surface of a semiconductor region through an insulating film and a structure for applying a predetermined voltage to these plurality of electrodes in consecutive order for transferring signal charges in a depletion region formed under these electrodes, that is, in a charge coupled device (CCD) is discussed in L. J. M. Esser, entitled "The Peristaltic Charge-Coupled Device for High-Speed Charge Transfer", ISSCC Digest of Tech. Papers, February 1974, pp. 28-29. It is stated in this literature that a well known CCD with a buried channel is provided in an epitaxial layer having a thickness of 4.5 microns and having the same conductivity type as a buried impurity layer which is formed on a substrate of a complementary conductivity type to that of the buried impurity layer for the purpose of improving charge transfer speed and transfer efficiency of a CCD.
A structure of providing a CCD in a well of a conductivity type which is complementary to that of a buried impurity layer formed on a substrate of the same conductivity type as that of the buried impurity layer is discussed in Y. Ishihara et al., "Interline CCD Image Sensor with an Anti Blooming Structure", ISSCC Digest of Tech. Papers, February 1982, pp. 168-169.